It is common to protect structures from fire for safety. In seismically isolated buildings the isolators are often an integral part of the structure. Thus, the isolators are to be protected from fire too. By nature of the isolation, an isolation space, usually the basement, moves along with the isolators. The isolation space needs fire proof partitions. These partitions separate the isolation space from the rest of the building as area separation walls. These partitions also need fire proofing, without restraining isolator movement. The isolators have wide horizontal and small vertical movements during earthquakes. Other times they have small horizontal displacements due to thermal expansion of the building. The fire rating assemblies at the isolation space need to accommodate all these movements. Such assemblies are advantageous around the isolators and around the isolation space itself. The isolation space is often closed by partitions. Furthermore, after a fire these are advantageously configured to pass the fire hose test; i.e. the high-pressure cold water right on or after fire. Inadequate assemblies may explode under such a severe test, which recently became a building code requirement in some jurisdictions. Similarly, the fire rating of seismic isolators, such as rubber bearings, is a new code requirement.
Recent efforts to fire rate isolators in the same manner as structures with sprayed asbestos have failed. Accommodation of wide isolator movements was not achievable this way. As long as isolators were placed in a crawling space right above the foundation, the isolation space did not need partitions. A sub floor, usually of concrete did the job. Recently, mostly in seismically retrofitted buildings, the isolators are placed over head in the basement. So partitions are needed to separate isolation and other usable spaces. A current solution to the problem is improvised on the field by contractors. The need for engineered, prefabricated assemblies is manifest.
Several fire rated wall and pipe penetration assemblies are known today. No such assemblies solve all the described problems altogether. Thus a reference could not be cited. The problem is the problem of a niche market.
Fortunately, building codes consider negligible the chance of a fire and concurrent earthquake. However, fire is assumed right after earthquakes due to broken gas pipes. Thus the assembly is desirably fire tested slightly offset, due to permanent isolator displacement. Wide offset fire testing is not required. It is assumed that the isolator movement due to earthquake is only seconds or minutes. The isolator movements are generally cyclic and therefore if during that cycling, fire would penetrate for only a second, that would not harm rubber isolators. Rubber isolators have a 1/2 inch cover layer to burn or deteriorate otherwise, before vital isolator parts would be harmed. Other isolators are mainly of steel construction and are even less sensitive to fire. Yet the toughest requirement remains: namely to allow for small, about 1/8 inch uplift, while some elastic means would compress the separation surfaces; but not too much, because that may destroy the edges of the retracted surfaces. At a retracted surface, usually one of the mating faces is covered with intumescent material, which expands upon flame contact. That expansion is needed to fill the unevenness of the gap for smoke and flame closure. The backing material of the intumescent advantageously comprises a compressible heat insulator, which is usually some type of ceramic fibre cloth. However, the heat insulator can not be compressed too much because it would loose insulation capacity very fast. Additionally, it would not retract fully or fast enough as the seismic isolator demands. The time mismatch is great. The isolator may also move with 2 to 3 seconds per cycle; and the insulator can recover about 80% compression strain in about 24 hours.